1. Field of the Invention
The present invention relates to a converging element and an illuminating device.
A generally used illuminating device used for a liquid crystal projector is formed of a lamp such a ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, and etc., and a parabolic reflector for collimating irradiating light from these lamps. In addition, to date, it is attempted to use a light-emitting diode (LED) as a light source (see Japanese Patent Laying-open No. 2002-189263).
FIG. 25A, FIG. 25B, and FIG. 25C show configuration examples of the light sources formed of a light-emitting diode. The Light source 400 shown in FIG. 25A has structure in which an LED chip is covered with a hemispheric resin (a hemispheric lens cover). Such the light source 400 needs a lens for controlling a dispersion angle of light due to its face that the emission light from the LED chip is dispersed. If a biconvex lens or a meniscus lens is arranged on a light-emission side of the light source 400, for example, it is possible to obtain approximately collimated light. In addition, a light source 401 shown in FIG. 25B is a light source having an angle control lens 401a of which outer curved surface is a total-reflection surface and of which light-emission surface is plane in shape (Japanese Patent Laying-open No. S61-147585). In addition, a light source 402 shown in FIG. 25C is a light source having an angle control lens 402a of which outer curved surface is a total-reflection surface and which is formed with a plurality of curved surface areas on a light-emission surface (such the light source 402 is offered by Lumileds Lighting, U.S. LLC).
FIG. 26 shows a light source 403 provided with an angle control lens 403a approximately same as the angle control lens 402a shown in above FIG. 25C. The angle control lens 403a is formed of a transparent material in a shape of a rotational symmetry, and includes a convex curved surface area (light-emission area) A formed in a center portion thereof, a peripheral curved surface area (light-emission area) B, a peripheral curved surface reflection area C, and a concave curved surface area (light-incidence area) D formed in the center portion. In the concave curved surface area D, an LED 403b having the hemispheric lens cover is provided.